Transmission electron microscopy of (001) ZnTe on (001) GaAs grown by molecular-beam epitaxy

Abstract

The structural properties of [001] ZnTe epitaxial layers grown on [001] GaAs substrates were investigated by transmission electron microscopy. The layers were deposited by molecular-beam epitaxy with thicknesses ranging from 50 to 1800 nm. The layers can be divided into three distinct regions of dislocation arrangements above the interface. The interface consists of an array of misfit dislocations. The separation of these dislocations is about 54 Å and is independent of layer thickness. The first region extends 300 nm towards the surface and consists of a tangle of dislocations. The density of these dislocations increases with layer thickness. The second region, between 600 and 1300 nm above the interface, was found to contain a low density of dislocations. Above 1300 nm, the third region, the dislocation density surprisingly increases again and in addition Te precipitates are detected near the top surface.